I think we are talking about a similar problem and perhaps the idea of thinking in terms of dimensions might help, but I don’t think it allows us to collapse things as far as ‘identifiable’:
Regarding dimensionality:
I think Ryan is right that we’re talking about many more dimensions that Tim had to consider, which might make the idea of dimensions less helpful – hard to think about infinite dimensional spaces versus a few dimensions like language and encoding.
Further, I don’t think they are ‘levels’ – our general case is not one where there are some fairly abstract things that just get defined/projected into fewer dimensions. We have cases where two high dimensional things partially overlap (my example of comet-currently-closest-to-the-sun was meant to convey this – it might be Halley’s at some point, but both Halley’s and the closest-comet have their own spatial extents and time evolution – one is not a lower dimensional view of the other.)
Regarding the nature of a bob:
I think some of the things that drove us to separate at least bob from stuff are still important, whether or not we chose to use dimensions as a way to explain the IVPof relationship:
People want to find bobs by their description (not just identifier) – to me this means our model has to include the idea of properties. If we punt and say that all means of discovering a particular bob – finding it based on its description to get to an ID, or using the ID to learn something about it – is out-of-band, I don’t think we have a usable standard. If there are alternatives to saying that bobs have properties with values that keeps this functionality, let’s get them on the table. (Do any of us think that pushing this functionality out-of-band is OK?)
IVPof does have the notion that there is real correspondence between the two bobs: B IVPof A. I think it is equally valid to talk about that correspondence in terms of saying that these two bobs overlap in some of the dimensions in which they are defined, or to say they represent the same stuff (because there’s something in the overlapping region of common dimensionality of these bobs). I see the idea of one bob being a lower dimensional projection of another being the same special case in which there are properties of A that are mutable that are fixed in B. Our general case has to include cases where the bobs are defined in terms of different coordinate systems over those dimensions (so their properties do not match) as well as where A and B overlap in some dimensions but each is also defined over some dimension(s) that the other does not share. (When Allen Renear (U. Illinois) visited recently, we had a fun discussion of the idea that only one thing can be in the same place at the same time – dimensional overlap as a way to define identity/equivalence. He brought up the example of talking about a statue versus the bronze in a statue as something that breaks this – I see this as a case where the bronze and the statue are each defined in dimensions the other is not, which is why we can’t see one as equivalent to or as a state of the other (not a hierarchical case)).
I think what that means in short is that if we try to describe everything in terms of dimensions, we don’t get something substantially simpler than we have now. TimBL’s model sounds simpler because he’s describing a simple subset of what we need to model.
Jim
From: public-prov-wg-request@w3.org [mailto:public-prov-wg-request@w3.org] On Behalf Of Luc Moreau
Sent: Friday, July 15, 2011 7:56 AM
To: public-prov-wg@w3.org
Subject: Re: simon:entity (or Identifiable)
Hi Ryan,
It's exactly where we were about 8 weeks ago. Your proposal seems to ignore
many agreements this WG has reached. We were using the word "R" then.
The reason why we moved into the direction of thing and IVP is that
there is stuff out there that is changing. For provenance, we need
something that didn't change from some perspective (or had some fixed
value).
For your proposal to work from my viewpoint, it needs to be more precise
about what is identifiable. Is it a stuff or is it a state of a stuff?
I note that all our discussions point to the fact that it is really
hard to distinguish a stuff from its state, since it is very much a
question of perspective. Still, we need to be precise about what is
identifiable. I think that the notion of properties associated with
old:thing/f2f1:BOB is reasonable way of providing the necessary precision.
Regards,
Luc
Regards,
Luc
On 15/07/2011 06:36, Ryan Golden wrote:
With apologies to Simon for hijacking his namespace, I'd like to take up Luc's suggestion to break off what he called the "simon:entity" proposal from the earlier thread into a separate thread.
Rationale
--------------
It should come as little surprise that some problems we are trying to solve by our design have been faced before by others in different contexts. After poring over the thread between Simon, Jim and others, I discovered a design issue discussion at (http://www.w3.org/DesignIssues/Generic), published by TimBL, which bears a _striking_ resemblance to the discussion we're having on stuff, thing, entity, entity state, and bob. While he does use the "R" word in some of the discussion, he makes the key observation that the identifiers we use every day have "multi-level genericity." That is to say, some identifiers are very specific ("Halley's comet, as viewed from the Hubble telescope, on 1/1/2014, in JPG format"), others more generic ("Halley's comet"). The Web design, he states, "should not arbitrarily seek to constrain life in general for its own purposes." Neither should we, I would argue.
Further, we may may make statements about "dimensions of genericity." That is to say that a) in relation to the thing it identifies, an identifier can be generic with respect to a particular dimension, e.g., in relation to the real Halley's comet, the "Halley's comet" identifier is generic with respect to time and content-type; and b) one identified thing may be generic in relation to another identified thing with respect to zero or more dimensions. TimBL talks about the relatively small number of dimensions of genericity for electronic resources, whereas we are interested in the infinite number of dimensions (i.e., all possible properties) over which identifiers and things in the world (not just electronic resources) may vary. The idea of "dimensions of genericity" gives what I believe to be a nice formulation for what we've been trying to discuss as "IVP of." I leave the remainder of this discussion to a separate thread, however (please post any comments on this paragraph to that thread).
If I fail to express some of TimBL's ideas adequately, I strongly suggest you read the Design Note--it is brief and more well-written.
Proposal
-------------
Given both elegant formulations, I would like to propose we conflate the following concepts:
old:stuff
old:thing
f2f1:entity
f2f1:bob
f2f1:entity state
Into a single concept:
simon:entity (alternate suggested name: "Identifiable")
Which can be described as:
that which an identifier represents
And, importantly for IVP of:
A simon:entity/Identifiable may exhibit a different level of genericity in relation to another simon:entity/Identifiable with respect to zero or more dimensions.
--Ryan